Pakistani security forces have arrested an al-Qaeda-linked militant wanted in connection with an assassination attempt on former prime minister Benazir Bhutto hours after she returned from exile in October.

Two-time prime minister Benazir survived the suicide bombing on a procession in Karachi after she arrived home on October 18, but nearly other 140 people were killed. Benazir was assassinated in a gun and bomb attack blamed on al-Qaeda-linked militants in the city of Rawalpindi on December 27.

The interior minister, Hamid Nawaz, said the suspect, Qari Saifullah Akhtar, was arrested early on Tuesday, along with his three sons, and was being interrogated about the Karachi attack.

'He was involved in the Karsaz bomb blast,' the minister said, referring to an overpass in Karachi where the attack on Benazir took place. In her book, Reconciliation, published after her murder, Benazir identified Akhtar as a 'wanted terrorist' who tried to overthrow her second government in the 1990s.

She also said he was involved in preparing the bomb attack on her procession in Karachi. Hashmat Habib, a lawyer for Akhtar, said he was arrested at a Muslim shrine near the eastern city of Lahore.

A former chief of the banned Harkat-ul-Ansar militant group, Akhtar ran a militant training camp in Afghanistan, a security official said.

Akhtar fled from Afghanistan after US-backed forces toppled the Taliban regime in 2001 and took shelter in Pakistan's South Waziristan tribal region on the Afghan border before he fled to the United Arab Emirates.

Akhtar was sent by the UAE to Pakistan in 2004 and was arrested and detained, but he was released in 2007, the lawyer said. The police have arrested four Islamist militants in connection with Benazir's assassination.